Abstract: [Problem] To provide a practical solid polymer fuel cell having high cell performance and excellent durability. [Means for solving] The polymer electrolyte fuel cell according to the present invention includes: a membrane electrode assembly in which electrodes each including a catalyst layer are joined to both surfaces of an electrolyte membrane; and a peroxide decomposition catalyst which is fixed to the electrolyte membrane and/or the electrodes and includes a hardly soluble carbide, a boride, and/or a silicide. The peroxide decomposition catalyst preferably contains a carbide, a boride and/or a silicide of a rare earth element, a transition metal element or a typical metal element.

Abstract: A fuel cell electrode catalyst includes: catalyst metal particles containing at least one of platinum or a platinum alloy; and support particles supporting the catalyst metal particles. The crystallite size 2r obtained from an X-ray diffraction image of the catalyst metal particles is 3.8 nm or less, where r represents a crystallite radius of the catalyst metal particles obtained from the X-ray diffraction image. The amount of CO adsorption Y (mL/g-Pt) on the fuel cell electrode catalyst satisfies Y?40.386/r+1.7586.

Abstract: A fuel cell electrode catalyst includes catalyst metal particles and electrically conductive support particles supporting the catalyst metal particles. In the fuel cell electrode catalyst, a proportion of a surface area occupied by the catalyst metal particles with particle sizes of 4.5 nm or less to a surface area of the catalyst metal particles calculated from a transmission electron microscope image is 5% or less.

Abstract: A fuel cell electrode catalyst includes catalyst metal particles and electrically conductive support particles supporting the catalyst metal particles. In the fuel cell electrode catalyst, a proportion of a surface area occupied by the catalyst metal particles with particle sizes of 4.5 nm or less to a surface area of the catalyst metal particles calculated from a transmission electron microscope image is 5% or less.

Abstract: A fuel cell electrode catalyst includes: catalyst metal particles containing at least one of platinum or a platinum alloy; and support particles supporting the catalyst metal particles. The crystallite size 2r obtained from an X-ray diffraction image of the catalyst metal particles is 3.8 nm or less, where r represents a crystallite radius of the catalyst metal particles obtained from the X-ray diffraction image. The amount of CO adsorption Y (mL/g?Pt) on the fuel cell electrode catalyst satisfies Y?40.386/r+1.7586.